(they're back : Gulf fritillary butterflies in Point Reyes Station)

This text was originally published by EAC in late fall 2016. Today I spent some joyous minutes at the scene with bright orange lepidopterans flurrying all around me.

A noteworthy wildlife phenomenon in downtown Point Reyes Station has recurred this year, after first attracting notice in 2012. It centers on a large, bright orange butterfly known as the gulf fritillary, a species that evolved in the Tropics. Yet here in chilly coastal California, fritillaries have reestablished an intermittent population--very locally. A small swarm of these gorgeous lepidopterans conducts life, quite actively on warm days, in front of the Old Creamery Building, at the corner of Mesa Road and Highway One. Why, and how? The answers reside in the landscape plants that ornament a miniature plaza near the West Marin Community Thrift Store. There a fence bordering big rose and juniper shrubs is thickly bedecked with passion flower vine (Passiflora species), and this is the gulf fritillary’s host plant. Flying adult butterflies, looking like shards of sunlight, busily interact with the Passiflora and one another, oblivious to people watching mere inches away. Two such people on a warm afternoon in mid-November were butterfly conservationist Barbara Deutsch and I. The information conveyed here is from Barbara’s vast storehouse of knowledge. Every activity in the fritillary’s life cycle is on display (to the practiced eye) on or near the passion flower. A female, slightly duller than a male, rests on a leaf to evaluate conditions that may favor survival for a single tiny egg—one of 300–400 that she will place. One or more males swoop in, seemingly eagerly. One dances above the female, invisibly sprinkling pheromones that communicate to her the value of his offering. Packaged in the spermatophores that he produces one-by-one, a male will deliver vital nutrients that strengthen an embryo. The female likely chooses a well-endowed mate and may even be able to hold several spermatophores inside her “purse” before drawing upon one to fertilize her eggs. Individuals exemplifying other stages of butterfly life are here, as well. Along with pinhead-sized yellow eggs on the foliage, caterpillars of several sizes (or instars) are busy feeding and growing. Affixed and seemingly still are not-yet-hardened pre-pupae and also the pupae, wherein occurs the big magic—metamorphosis.

Coming and Going… or Staying

This butterfly’s range extension up the West Coast, over time, may have accompanied the arrival of new citizens from Mexico, who planted passion flower for its food, medicine, and ornamental values. Gulf fritillaries have been sighted as far north as Canada and, by the 1960s, appeared in San Francisco, along with Passiflora. The vine that supports fritillaries in Point Reyes Station is decades old, and so is a dense patch of passion flower in Valley Ford where these butterflies also live. Key to fritillary survival in our moist, cool bioregion are the size and thickness of the host vine, along with other attributes of a site. In Point Reyes Station the neighboring shrubs, a southern exposure, and factors in the built environment all contribute to the habitat, such that fritillary adults and caterpillars can shelter in the Passiflora to live through freezing nights.If the foliage is cut or dies back at a critical time, the fritillary population may crash, as evidently happened here in approximately 2014. However, a well-used vine remains a signpost for wandering butterflies. Drawn to quality habitat, they will home in on chemical traces left on the host plant by past generations of fritillaries. Enough of them convened here this year to manifest a beautiful renewal. This is change in progress, with the possibility that gulf fritillaries can dwell in Point Reyes Station year-round—essentially permanently! The same potential exists for many a butterfly species if it can find, in the wild or cultivated by people, the particular host plant and habitat features that it requires.